DIY EEG Amplifier- something went wrong...

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ml_235

Joined Nov 2, 2019
4
I have tried making an EEG circuit from:
https://www.instructables.com/id/DIY-EEG-and-ECG-Circuit/
I have made the circuit and tested it various times, however I don't get any kind of values. The batteries, electrodes and the cable going to the laptop function properly and circuit was checked various tymes, however I still get all the values as 0. The electrodes conduct 9v properly, however they are DIY, could that be the cause? I have checked the output capble and there's some voltage coming out, but the codde shows nothing, just like when you run it without connecting anything. If any of you has any possible idea of what could have gone wrong, pleaseeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee consider letting me know. PLEASEEEEEEEEEEE!!! ASAPWhatsApp Image 2019-12-16 at 13.03.31.jpegCapture.PNGWhatsApp Image 2019-12-16 at 13.03.35.jpeg
 

Alec_t

Joined Sep 17, 2013
11,296
Welcome to AAC!
I have checked the output cable and there's some voltage coming out, but the code shows nothing
I don't know what you mean by that. How did you check the output? What is 'the code' supposed to do?
Breadboards are notorious for causing problems due to wiring errors and non-existent, intermittent or poor connections. I'd be checking there first.
If you are using a standard PC sound card, be aware that some have a frequency response which drops off sharply below about 20Hz.
 

MrChips

Joined Oct 2, 2009
21,126
I see many things wrong.

Starting with the first photo, I see some kind of glue on the 9V battery clips. Get proper battery clips with wires properly connected.

The worst thing is the prototyping breadboard. As already mentioned, there are lots to go wrong with a breadboard. Even if you got all the connections right, you have little hope of amplifying very weak signals such as ECG or EEG. You need to put the circuit on to a PCB with proper shielding and not a plastic case.
 

Audioguru again

Joined Oct 21, 2019
1,493
I agree that you should get rid of the "Mickey Mouse" breadboard.
I wonder why the Instructables student used TL082 dual opamps, each one with an unused opamp not terminated? The unterminated opamps could be oscillating or worse. Instead, TL081 single opamps should have been used.
 
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